Dark Matter Expert

---
name: dark-matter-expert
version: 1.0.0
description: Expert-level dark matter physics covering observational evidence, candidate particles, detection methods, structure formation, and alternative gravity theories.
author: luo-kai
tags: [dark matter, WIMPs, axions, direct detection, structure formation, gravitational lensing]
---

# Dark Matter Expert

## Before Starting
1. Particle physics or astrophysics perspective?
2. Detection method? Direct, indirect, or collider?
3. Specific candidate particle?

## Core Expertise Areas

### Evidence for Dark Matter
Galaxy rotation curves: flat curves require mass beyond visible disk.
Gravitational lensing: mass inferred from light bending exceeds visible mass.
Bullet Cluster: separation of X-ray gas from lensing mass in cluster collision.
CMB: acoustic peaks encode dark matter to baryon ratio.
Structure formation: CDM model successfully predicts large-scale structure.

### Candidate Particles
WIMPs: 10 GeV to 10 TeV mass, weak interaction cross section, thermal relic.
Axions: ultralight, motivated by strong CP problem, cavity experiments.
Sterile neutrinos: right-handed neutrinos mixing with active neutrinos.
Primordial black holes: formed in early universe, constrained but not ruled out.
FIMPs: feebly interacting massive particles, freeze-in production mechanism.

### Detection Methods
Direct detection: nuclear recoil in underground detectors, LUX, XENONnT, PandaX.
Indirect detection: annihilation or decay products, gamma rays, neutrinos, positrons.
Collider production: missing energy signatures at LHC, monojet events.
Astronomical: perturbations to stellar streams, substructure in galaxy halos.

### Alternative Theories
MOND: modified Newtonian dynamics, acceleration-dependent force law.
MOND success: fits galaxy rotation curves with one free parameter.
MOND failure: galaxy clusters require additional dark matter even with MOND.
TeVeS: relativistic MOND extension, difficulties with CMB and gravitational waves.

## Best Practices
- Consider full range of mass scales for dark matter candidates
- Account for astrophysical uncertainties in direct detection limits
- Distinguish robust evidence from model-dependent claims
- Use model-independent approaches where possible

## Common Pitfalls
| Pitfall | Fix |
|---|---|
| WIMP-centric view | Many viable candidates exist at different mass scales |
| Ignoring local density uncertainty | Direct detection rates depend on local DM density |
| Dismissing MOND entirely | Explains individual galaxies well, fails at cluster scale |
| Confusing exclusion limits with detection | Null result sets upper limit only |

## Related Skills
- cosmology-expert
- astrophysics-expert
- physics/particle-physics-expert